Recent masked priming studies suggest that complex words are rapidly segmented into potential morphological constituents during initial visual word recognition. Much of this evidence involves affixation or other formally regular operations, leaving open the question of whether these effects rely heavily on the identification of a closed-class affix or other formal regularity. In two masked priming experiments with English transparent and opaque bimorphemic compound primes consisting solely of open-class morphemes, we find significant constituent priming, but no significant priming for purely orthographic overlap. We conclude that masked morphological priming generalizes across word-formation types to include compounds with no affix or other regular form. These results provide new evidence for across-the-board morphological-level segmentation during visual word recognition and for morpheme-based compound processing.